Centrifugal air compressor



De. 11, 1945; A. L BERGER cENTnIFUGAi. yAIR COMPRESSOR Filed oct. 2o'. 194:5

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Patented Dec. 11, 1945 UNITED STATES PATENT GFFICE 2,390,504

CENTRIFUGAL AIR COMPRESSOR Adolph L. Berger, Dayton, Ohio Application October 20,1943, Serial No. 506,979

(Cl. 23d-127) (Granted under the act o! March 3, 1883, as amended April 30, 1928; 370 0. G. 757) 4 Claims.

The invention described herein may be manufactured and used by or for the .Government for governmental purposes, without the payment to me of any royalty thereon. f

This invention relates to centrifugal air compressor iort high speed turbo-blowers and pumps, and has for an object, means to reduce or eliminate turbulence in the fluid being pumped as it leaves the centrifugal impeller member of the pump and passes into the peripheral portion of the blower casing.

Centrifugal impellers of the turbo-blower type, used for supercharging aircraft internal combustion engines at high altitudes'operate at extremely high speeds and the air being pumped or compressed travels through the impeller at an extremely high velocity; and it is diilicult in the usual centrifugal pump of the turbo-blower type to effect a smooth and uniform fluid ilow, particularly at the tip or periphery of the impeller member, and in the zone just beyond the impeller periphery where the compressed fluid passes into the annular iluid collection and delivery chamber of the impeller casing, which has the discharge i opening leading to the intake manifold or other fluid delivery point.

One reason for the non-uniform flow is that the space between the side plate or shrouds of the impeller member and the adjacent sides of the casing usually constitutes a low pressure area, and

the frictlonal drag or skin friction of the fluid bea comparatively low pressure area extending beyond the periphey of the impeller member. The main air ilow from between the shrouds of the impeller, as it leaves the impeller is eifected by the movement of this recirculated air, and the low pressure area at the tip or periphery of the impeller at opposite sides of the main fluid flow, tends to withdraw or disturb the outer layers of the main fluid delivery from the impeller producing eddies or turbulence in the main flow a-nd with a marked reduction in the eiciency of the impeller. This decrease in efllciency becomes greater as the velocity of the compressed fluid increases. 4 v

Auxiliary vanes have been employed on the exterior surfaces of centrifugal impellers of certain Athe region of the periphery, disturbing the boundary liow of air between each silde of the impeller member and the main fluid ilow, as it leaves the periphery or tip of the impeller member. As a result, eddy currents are created in the fluid flow producing the undesirable turbulence and corresponding decrease in impeller elciency.

` Another object is the provision of means preventing recirculation of the iluid being pumped by the impeller member, between the sides of the impeller member and the inner walls of the casing,

to obtain a smooth and uniform iluid flow ofthe pumped fluid as it leaves the impeller member.

A further object is the provision of a high speed shrouded centrifugal impeller for delivering a normal volume of fluid under pressure, having auxiliary pumping means on the impeller for delivering an auxiliary volume of fluid under pressure at opposite sides of the main volume of fluid, to form boundary layers of fluid at opposite sides of the main volume to eliminate the usual reduction of pressure at opposite sides of main iiuidvolume, due to the skin friction or drag on the fluid at opposite sides of the impeller and casing, and to eliminate the tendency of recirculation of the fluid being pumped between the impeller shrouds, and as the iluid leaves the periphery of the impeller and passes into the casing, to effect a uniform ilow, with the elimination of turbulence adjacent the tip or periphery of the impeller member with a corresponding increase in the efliciency of the pump device.

A still further object is the provision of a; shrouded impeller member having iluid conducting means for establishing a fluid circulation between the shroud Vmembers of the impeller member and the space between the shroud members and the adjacent inner surfaces of the impeller casing, for introducing a portion of the fluid being Pumped into the last mentioned space to eliminate or reduce the usual low pressure area between the impeller and casing, particularly at the periphery of the impeller, with corresponding elimination of the eddies and turbulence in the fluid being pumped as it leaves the impeller member that are caused by the said low pressure area at the impeller periphery.

respective sidewalls II and I2 with the'annular .s0

member- 2 is located inwardly of lthe-juncture of 65 Other objects and advantages of the invention I will hereinafter become apparent from the accompanying specification and claims. taken in conjunction with the accompanying drawing, in

which like reference characters refer to like parts 5 in the several figures thereof.

Fig. 1 is a vertical sectional viewthrough my improved high speed turbo-blower.

Fig. 2 is an enlarsed cross sectional view taken approximately on the plane indicated by the line lo I indicates a drive shaft for a high speed turbo- 20l blower device, and 2 afcentrlfugal impeller mem ber having. a central hub portion 3 nxedly secured on the shaft to rotate therewith.

The impeller 2 is formed with front and rear plates or shroud members I and l. respectively, 25

havingmain impeller vanes or blades I extending between the front and rear shroud members Ji and l. Main uid inlet ports I are formed in the front shroud member 5, and the adjacent, or in-V ner surfaces ofthe front and rear walls or shroud 30 members 5' and 6 curve rearwardly and outwardly. tapering toward'each other 8nd terminate in reduce radial outlet ports 9 located between the` vanes or blade members 1.

The impeller member 2 is journaled to rotate 35 within an'impeller housing or casing, indicated generally at I0, having spaced annular front and rear walls II and I2. The shroud members I and t of the impeller member rotate in spaced relation to the walls II and I2, and the rear wall I2 40 extends inwardly to a point adjacent thashaft I to form a central opening I2 surrounding the shaft I in'spaced relation thereto for admitting air, or the fluid being pumped, into the space between the rear faceof the impeller shroud mem- 4c ber 6 and the rear wall I2 of the impeller casing.

The front wall II of the casing is formed with a large central opening Il, in register with the inlet ports 8 in the impeller and has an annular opening Il' to introduce air, or the pumped fluid, so

into the space between front shroud member I.

and the inner surface of the front wall II of the impeller casing I0. The impeller casing is provided with an an` nular chamber Il, substantially circular in cross 55 section surrounding the periphery of the walls I I and I2 andis preferably provided with a tangential iiuid'outlet or peripheral discharge port Il'. Curved annular wall portions connect the chamber Il, providing for a smooth airflow surface along the inner surfaces of theV walls II and I2, and intolthe annular chamber Il.

The periphery or tip portion of the impellerthe side walls II and I2 of the impeller casing III with the curved annular wall portions Ii and Il, and the inner surface of the annular charnber Il. The shroud members I and i operate in spaced relation to the inner walls Il and I2 of "1 the impeller casing and the exterior of the shroud members 5 and are each provided with a suit.

' able number of auxiliary impeller blades or ribs II and I8, projecting 'toward the adjacent surassures mg and terminating in Y said surfaces.

juxtaposed relation to The auxiliary blades or vanemembers I1 and I8 cause an auxiliary flow or circulation of the air being pumped to pass through the openings I2 and Il into the spaces between the impeller mem-ber 2 and the inner surfaces of the walls II and I 2 of the .impeller casing 'as the main air flow of the compressed air, or the pumped fluid medium passes into the inlet openings 8 through the curved throat or chamber and into the space between the plates or shroud members 5 and t of the impeller 2, between the main blades 1, and this air or iluid is discharged through the dis-l charge openings 9 at'the tip or periphery ofv the impeller. p

The iiow of air at opposite sides of the main air flow, caused by the auxiliary-blades I1 and Il, producesboundary flows or layers of air at predetermined pressures at thetip or periphery of the impeller 2, effecting a smooth streamline or uniform iiow of the air as it leaves the main blades 'I of the impeller member and passes into the annular Vdelivery chamber Il. This ow of auxiliary or boundary air at opposite sides of the casing and main airilow smooths out the main ilow, eliminiating recirculation or turbulence in 1 the main ow with a corresponding greater efficiency in the operation and output of the impeller device.

The auxiliary air intake openings I2' and I2' may be somewhat restricted in area to produce a controlled flow of air, with asomewhat lower pressure area., intermediate the auxiliary inlet openings I 2 and I3' and the discharge point at `the periphery of the impeller member. This reduction in pressure between the sides I and 8 of the impeller and the sides of the casing reduces the frictional drag .on side platesv of the impeller, and even thoughth air delivered by the auxiliary blades I1 and I8 at opposite sides of the airflow from the main blades 1. may.be under a lower Vcompression than the main air now, the auxiliary flow has a tendency to expand after leaving the tip of the impeller, as it merges with the main flow, will cause the aforementioned boundary layers at-opposite sides of the main air flow to eifect a smooth and uniform iiow of the air ilow as it passes into the annular chamber Il and is discharged at I4' from the pump.

Referring to rig. 1 or the one of the vside plates of the impeller may also be apertured as indicated at 'I9 to provide inlet es or openings admitting air or the fluid being pumped intothe space between the side plate 6 and the adiacentsurface of the impeller casing. These apertures I9 are located at points between the periphery of the impeller 2 and its central or hub portion I to provide means for introducing' -a portion of the fluid. entering main throat l into the zone of the auxiliary blades I8 at the innel ends of these blades. 'Ihe auxiliary blades Il cause this air to be projected from between the impeller and casing at the periphery of impeller, at the side of the main flow, between the main flow and the limpeller casing, eliminating I the low pressure-area usually occurring at the periphery of the impeller, and preventing the formation of eddies in the main ilow where it leaves the rim of the impeller which ordinarily occur and cause turbulence lin the main air flow. The frontshrouds l may also be provided with openings similarto the openinsallinthe rear faces of the wens and' iz'or the impeller car 7 if u is desired, but as the rim or the:

central opening in the front shroud is located about at the point I3' where the inner ends of the vanes or ribs I1 are located the auxiliary air can readily be admitted through the narrow annular opening I3', into thel space between the front shroud 5 and the adjacent inner surface of the casing in the zone of the fron-t auxiliary blades I1 A further modication of the invention is disclosed inrFigs. 3 and 4 in which the impeller member, as indicated at. 20, if formed with a rotary single flange or disc member 2| having main impeller blades 22 extending forwardly toward the front wall of the impeller housing, and auxiliary blades 23 projecting from the rear face of the impeller member toward the rear wall of the impeller housing. 'Ihe rear or auxiliary blades supply the auxiliary air flow or boundary layer to the rear portion of the main iiow, as before described, with the same increased efliciency and lack of turbulence in the air flow at this point as previously set forth Instead of utilizing a front shroud member with auxiliary blades thereon to vsupply the other or front boundary layer of air to the mairr air flow, I provide a plurality of tubular members 2l of a somewhat tapered and curved formation, substantially rectangular in cross section. These tubular members' are preferably made of light sheet material and formed to t into the spaces between the main impeller blades 23, with their Ysides 25' constructed and arranged to lie infspaced relation to the inner surface of the adjacent front wall,

of the impeller casing, when the. impeller is positioned therein. The walls 25 of the tubular members 24 form and constitute a second shroud member in effect, with the extremities 26 of the main blades 22 projecting out beyond the walls 25 constituting, in effect, auxiliary blades or vanes adjacent theinner surface of the front wall of impeller casing providing means `for supplylng the other, or front boundary layer of air for the main air ilow at the impeller periphery and as it leaves'the impeller and enters the annular delivery chamber Il, eliminating any tendency for recirculationl or turbulence in the main air dow.

,Having thus described my invention, I claim, 1. In a high speed centrifugal impeller-of the class described, a circular casinghaving opposite front and rear walls smoothly blending into an enlarged annular peripheral chamberhsubstantially circular in cross section, having a tan- 4 gential fluid outlet, one of said walls having a central uid inlet opening therein, an impeller member concentrically rotatable within the casing between the front and rear walls thereof comprising spaced annular shroud members having 'their peripheries disposed inwardly of the saidA annular peripheral chamber to leave an annular space between the peripheryof the impeller and said peripheral chamber, and disposed in spaced rear walls of the casing for inducing an auxiliaryA boundary layer flow of the fluid being pumped, along each adjacent side wall of the casing to be delivered in a plane parallel to theplane of rotation of the impeller at the peripheryof the impeller memberlat each side of the main fluid flow relation to the side walls of the casing, one of from the main impeller blades between the same -and the front and rear walls of the casing to proturbo-blower type, a circular casing formed with i an enlarged annular peripheral chamber, substantially circular in cross section and having spaced front and rear circular walls with their peripheral portions curving smoothly outwardly and merging into said annular chamber, said circular front wallhaving a substantially centrally located' uid inlet port, impeller means rotatably mounted within the casing comprising spaced annular side plates having their peripheries disposed radially inwardly of the said annular charn-A ber and in spaced relation to the side walls of the casing to permit the fluid being pumped to flow therebetween, main impeller blades extending between the said impeller side plates, auxiliary impeller blades extending from the side platesand terminating in juxtaposed relation to the inner surfaces of the adjacent side walls of the casing, for inducing an auxiliary boundary flow of the fluid being pumped by the impeller to flow radially outward along each side wall between the same and the casing to deliver said auxiliary flow in a radial direction at the periphery of the impeller member uniformly along the sides of the casing at each side of the main fluid flow to effect a uniformly moving boundary layer of fluid at each side of the main fluid flow next to the casing side walls to reduce turbulence of the iiuid being pumped as it leaves the impeller member and passes into the annular chamber, one of said impeller member side plates having radially inclined fluid conducting passages formed therein extending therethrough inwardly of its periphery be- Y tween the auxiliary blades and intermediate the ends of the blades for establishing a uid delivery conduit between the space between both impeller side plates, in the zone of the main and auxiliary impeller blades and the space between the side plate having the fluid conducting passages therethrough and the inner wall ofthe casing adjacent said latter plate.

3. A centrifugal impeller member for fluid pum'ps of the class described comprising a rotary shroud member having a plurality of main vane members projecting laterally from one face of the shroud member in a direction from the center to the periphery to form fluid passagestherebetween and a plurality of auxiliaryl vane members projecting laterally from the opposite face of the shroud member in a direction from the center toward the periphery to form auxiliary fluid passages therebetween, insert members disposed on the impeller member between the main vane member, each having a. wall extending between the adjacent main vane members in spaced relation to said shroud member and terminating in angular side portions disposed against the opposite faces of the main vane members with the walls of the insert members disposed in a plane located between the plane traversed by the lateral edges of the main impeller vanes and the adjacent surface of the shroud member to leave ex-v terior auxiliary fluid conduits extending lalong the said insert members. between the vane members, and an impeller casing, surrounding the said impeller member having side plates disposed adjacent the sides of the impeller member with the said auxiliary uid inlet passages introducing boundary. myers of the fluid being" pumped at prima!A te sides of the num passing through said insert members, introducing boundary layers-of the pumped uid flowing along the sides ofthe casing in' the same direction as the main uid flow.

4. A centrifugal impeller member for :fluid pumps ofthe class described comprising a rotaryshroud member having a plurality of main lminsert members disposed on the impeller member between the main impeller vane members, each having an outer wall portion extending between the adjacent vane members in spaced relation to through the lateral edges ofthe main vane members intermediate said edges and the shroud member, to form main uid conduits within -the tubular members, auxiliary boundary layer uid conduits between the main vane members and the aforesaid edges, and an impeller casing, housing said impeller member having side plates disposed adjacent the sides of the impeller member and iiuid inlet openings for'med therein for introducing the iluid to be pumped at opposite sides of the impeller member, and into the interior-of thei tubular members.

' ADOLPH L. BERGER. 

